'The male sets off in pursuit of the female tortoise," said David Attenborough world-wearily. "He'd be able to mate with her if only he could get her to stand still." If there's anything in the natural world less exciting than a Madagascan tortoise chase, not even Attenborough's researchers have found it yet.

Finally, the male caught up. On sofas around Britain, people nudged significant others back into consciousness to see what happened next. "He uses the front of his shell to lift her back legs off the ground. She seems less than willing. It's a slow process, but radiated tortoises don't do anything quickly." They even take a long time to die – there are reports of a 188-year-old male radiated tortoise who, you'd suspect, hasn't used his Marvin Gaye albums in courting rituals for ages.

Not for the first time in Madagascar (BBC2), I wondered how the sex lives of the BBC's Natural History Unit would stand up to primetime satire. Earlier, Attenborough had intruded on the mating rituals of giraffe-necked weevils and later had commented, rather sniffily, on how the female fosa (a giant mongoose) had perched 15 metres up on a branch "advertising her availability to her suitors. This is the sixth male she's entertained today."

How many lemurs remain unfilmed by the BBC? Two, maybe? There are 80 species of lemur on Madagascar and last night it seemed possible that Attenborough was going to explain how each one of them had adapted to the many landscapes of what he called "this curious wonderland".

Not that I'd have minded: some measure their lives in coffee spoons; I measure mine in lemur footage. I enjoyed seeing again how the sikar lemur gavottes on hindlegs across treeless terrain, front paws aloft – like a fey footman bearing an urgent telegram for Hugh Bonneville on Downton Abbey.

At some point, I dozed. When I woke up, I'd died and been sent by mistake to hen heaven. All I could see was an other-worldly beach covered with broken egg shells. But no: this was a beach in Madagascar where 1,000 years ago the three-metre tall elephant bird strutted its funky stuff. What was striking was that Attenborough produced no computer-generated elephant bird to show us what the super-sized dodo who laid these eggs (each one bigger than a dinosaur's) looked like.

This was a bold omission, not least because the best of the night's TV spent a lot of computer power recreating the past. In Romancing the Stone (BBC4), for instance, Alastair Sooke taught us that the majestic west front of Wells cathedral would have been richly coloured in medieval times. To clinch his point, CGI colour spread across the front on our screen, backlighting the Virgin in blue, illuminating saints and Anglo-Saxon martyrs in gaudy hues. I'd only imagined the gothic stone in monochrome before. Here it became as visually clamorous as a night-time view of downtown Tokyo.

Sooke had a tough task convincing us that the period from the Norman conquest to the reformation was a golden age for British sculpture because 90% of it was destroyed by Henry VIII's henchmen. But he ardently eulogised the 10% that remains – such artworks as the Arundel tomb in Chichester cathedral, so beautiful that it melted even Philip Larkin into fond poetry.

In A History of Ancient Britain (BBC2), Neil Oliver similarly put computers to work to show how Britain was sculpted on a geological scale. Magically, the CGI blob on screen became filigreed Scottish coastline as the ice retreated. Britain's newborn north-eastern coast shrugged off Scandinavia. Lower down, a vast peninsula still bound southern Britain to the continent, like a Eurosceptic's nightmare.

Not for long. In 6100BC a 10 metre-high tsunami wept over Montrose and raced 40km inland, definitively detaching us from Europe. Oliver didn't have the budget to recreate that.

This proved a demanding hour in which the visuals couldn't keep pace with the epic narrative. Paddling off Gwent, Oliver found a muddy footprint. He insisted it was "fragile and poignant evidence" of human life 8,000 years ago. "That's one of the best things I've seen," said Oliver. Lucky archaeologists: they see the world through enchanted eyes. To mine, it looked like a dog walker's footprint from five minutes earlier.